As someone who types constantly, I am always looking for shortcuts. It frustrates me when highlighting text that oftentimes a multi-line sentence can be easier to highlight than a single -line sentence. This is due to the fact that if one's cursor is at the end of a multi-line sentence one must press
shift-up repeatedly (the number of times the sentence has lines.) The sentence is quickly highlighted. In the case of a one line sentence a person has to press Shift-left repeatedly (the number of times there are characters.) This is bound to take longer since there are usually more characters than there are lines. Inefficiency here is clear.

Regardless. Alt-A is just too out of the way, and highlights to the beginning of the paragraph (often more than I need.) Why not add efficiency and make the highlight sentence quick key: Shift-Up.

[Kenry52]: Highlighting things with a mouse - using mice in general - requires a lot of hand/eye coordination and puts strain on your eyes and your shoulder; it also requires you to move your arm from the home position on the keyboard. It's slow, too. It doesn't feel slow - so much is going on - but it is, and you'll feel yourself relax more if you learn the keyboard short cuts for your most frequent tasks.

[I've never heard the theory that this is gender-specific; do you have a reference for that, ConsulFlaminicus?]